ONYCHOPHORA AND MYRIAPODA 



275 



United States in houses. It is slightly compressed laterally, has long 

 legs, and runs with great speed. It is a beneficial form, since it preys 

 upon various noxious insects, such as cockroaches and bedbugs, which 

 live around houses. 



Fig. 178. — The long-legged house centipede, Scutigera forceps. When a few of its 

 numerous legs are seized and held the centipede instantly detaches its body from these 

 legs and flees to safety on its remaining legs. In about a month it will regenerate new legs 

 to replace those that were lost. If, however, it is irritated sufficiently, it will detach all 

 of its legs, and then accelerating its regenerative processes will produce a full set of new 

 legs in about two weeks. Ranges from southern United States as far north as New York 

 and Nebraska. (From Marlatt, Farmer's Bulletin, No. 627, U. S. Dept. Agriculture, 1914.) 



310. Millipedes. — The millipedes, or thousand-legged worms (Fig. 

 179), differ from the centipedes in several ways. The body is sub- 

 cylindrical rather than flattened. The legs are very short, generally two 

 pairs to a segment, and the animal tends to react by rolling up into a flat 

 coil instead of by running away. There is a pair of mandibles and one 

 of maxillae, and either simple or compound eyes. The millipedes also 



Fig. 179. — A millipede, Spirobolus sp., from South Carolina. 



Natural size. 



From a preserved specimen. 



live in dark, moist places but feed principally upon plant food and 

 therefore are likely to be injurious, whereas the centipedes are likely to 

 be beneficial. 



311. Reproduction in Myriapods. — In all myriapods the sexes are 

 separate. Some millipedes are known to lay large numbers of eggs in 

 cells excavated in the ground, which are later sealed up, but in the 

 case of the centipedes the eggs are laid singly in the damp earth. The 

 larva when hatched has only a few metameres and a few legs. The larvae 

 of the millipedes have only three pairs of legs, in this respect resembling 

 insects. As the animal grows, new metameres, each with a pair of legs, 

 are added just in front of the posterior one. Thus the total number of 

 metameres in the body is an indication of the age of the individual. 



